Ax, you are f*cked. If you tell PayPal that you accepted a gift for merchandise it is possible that PayPal will freeze your account. I know you mentioned earlier that you might not use PayPal anymore but is that really an option? I assume that you buy and sell a lot online. PayPal is pretty much the method that most buyers and sellers use.
You might one option. Did you ship these items USPS? If so I would consider a mail fraud complaint if the buyer didn't send the items back. I have had two cases where I had to file a mail fraud complaint. Both of those people are now in jail.